1. Field of the Invention
The present invention relates to an electron beam lithography method for performing lithography exposure of elements included in a pattern by use of an electron beam onto resist provided on a disk to form an uneven pattern and the like of a master carrier for magnetic transfer during manufacture of the master carrier for magnetic transfer and the like.
2. Description of the Related Art
A magnetic transfer method for transferring and recording a magnetization pattern corresponding to information (for example, servo signals) carried by a master carrier for magnetic transfer onto a slave medium is known. The magnetization pattern is transferred by applying a transfer magnetic field in a state where the master carrier and the slave medium closely contact with each other. The master carrier carries transfer information by means of a fine magnetic uneven pattern and the slave medium has a magnetic recording part for receiving the transfer.
As a method for manufacturing the master carrier used in this magnetic transfer, applying a method for manufacturing an optical disk stamper is being considered. In this method, a master carrier is manufactured based on a master disk having an uneven pattern formed thereon by use of resist corresponding to information to be transferred (for example, see U.S. Patent Laid-Open No. 20010028964.)
In manufacturing the above-described optical disk stamper, resist is applied to a disk (a glass plate or the like) Data are converted into lengths of pits, and written into the resist by irradiating the disk with a laser beam modulated according to the converted data while the disk is rotated.
In the case of manufacturing the master carrier for magnetic transfer also, performing lithography of a micropattern by irradiating a laser beam modulated according to information to be transferred while rotating a disk having resist applied thereto is generally considered, similarly to the manufacture of the above-described optical disk stamper.
However, manufacture of miniaturized and higher-capacity magnetic disk media is being attempted. When a bit length or a track width is narrowed in accordance with an increase in recording density (for example, when the bit length or the track width becomes 0.3 μm or less), the lithography diameter approaches the limit of a diameter capable of being exposed by a laser beam, and ends of drawn portions come to have an arcuate shape. Accordingly, it becomes difficult to form rectangular elements of a pattern. Particularly, an upper surface of each element included in a pattern formed in a master carrier has a shape corresponding to this drawn portion. When the ends of the drawn portions have the arcuate shape, the upper surface of a protruded portion of the uneven pattern on a master carrier board has a shape greatly different from a rectangular shape, such as an arcuate shape. Accordingly, it becomes difficult to form a desired magnetization pattern in a slave medium.
Meanwhile, in the field of semiconductors, patterning utilizing an electron beam capable of performing exposure by use of a spot having a smaller diameter than that of the laser beam is being performed. The use of this electron beam enables highly accurate patterning of a micropattern.
Moreover, in manufacturing of patterned media expected to be realized as miniature and light weight high-density magnetic recording media, it has been proposed to perform pattern exposure by use of an electron beam (for example, see Japanese Unexamined Patent Publication No. 2001-110050).
In manufacturing of the above-described master carrier for magnetic transfer and patterned media, it is required to perform concentric patterning. Therefore, good pattern formation is difficult by direct application of an electron beam lithography method using an XY stage, which is utilized in the field of semiconductors. For this reason, an electron beam lithography method capable of good pattern lithography is desired. Moreover, in achieving a higher-capacity optical disk, since there arises a problem similar to that of the above-described master carrier for magnetic transfer, an electron beam lithography method capable of drawing a spiral micropattern is likely to be required.
In the lithography of such a micropattern as described above, the number of lithographic elements becomes enormous along with an increase in the number of tracks (the number of sectors). Accordingly, there are demands for shortening of lithographic time by improving a lithographic speed, for improvement in a lithographic shape and lithographic position accuracy in the entire disk region, and for uniformity of exposure. Particularly, in drawing a concentric or spiral micropattern while rotating a disk, it is required to cause element forming positions corresponding to rotation phases of the disk to be continuous from an inner periphery side to an outer periphery side. In addition, accuracy of a length of an element in its circumferential direction is required.
For example, in the case of a micropattern of a CAV type, the rotational speed of a disk is constant. Therefore, when recording the same data in both inner and outer periphery sides of the disk, lengths of lithographic elements in the circumferential direction have to be formed shorter in the inner periphery side and longer in the outer periphery side. Accordingly, it is difficult to secure the formation accuracy thereof. Moreover, when recording, for example, servo signals, it is difficult to cause origins of elements at the inner and outer periphery sides to coincide with a reference position of a rotation phase. Moreover, due to accumulation of errors and the like, it is difficult to dispose a number of patterns at even intervals within one lap of the disk.
Further, in exposure using the electron beam, element formation accuracy is also influenced by lithography using a uniform exposure amount corresponding to sensitivity of resist on the entire surface of a disk. However, control thereof is complicated in relation to a rotation speed and the like.